The present disclosure relates to printing systems, more specifically, to a system and method for matching colorimetric attributes of a production print to a proof.
Print buyers or document designers do not always have access to digital production printers, such as the XEROX DocuColor iGen3 Digital Production Press. As such, during the course of designing a document for subsequent printing using a production printer, the document designer creates proofs for visualizing how a final, production print will appear. These proofs are often created using any of a number of printers (DFE/IOT) more suitable for an office environment, such as a desktop inkjet device.
The created proofs generally set expectations for the designer or the print buyer as to the colorimetric attributes and final appearance of the production print. When the designer or print buyer likes a particular proof, an electronic application file corresponding to the particular proof is then submitted to a press or other facility having a production printer for producing a production print corresponding to the proof. Upon submission, the operator of the press is requested to “match” the proof, especially the colorimetric attributes of the proof, with the production print such that the production print substantially matches the proof. The colorimetric attributes refer to parameters and aspects which affect the color rendition of a print, such as brightness, contrast and hue.
Typically, an operator of a production printer has two options. One option is to explain to the designer or print buyer that the office or desktop printer that was used to create the proof produces prints which have different calorimetric attributes than the colorimetric attributes of prints produced by the production printer, and therefore, the colorimetric attributes of the print cannot be matched to the calorimetric attributes of the proof. The second option for the operator of the production printer is to use trial-and-error and attempt to set up the production printer with digital settings which would produce a production print which would more closely match the calorimetric attributes of the proof. This option requires the operator to spend time and effort to set up the production printer in an effort to closely match the calorimetric attributes of the proof.
The second option can be fruitless as there are typically physical limitations as to how close the color attributes can be matched. For example, the proof and the production print may have very different physical marking characteristics, e.g. inkjet versus toner, paper stock, and dye choices of colorants.
The operator of the production printer cannot usually make a “copy” of the proof, since the proof is likely to have lower IQ than what is available on the production printer (streaks, bands, error-diffusion dots, lower resolution, etc.), and may even be damaged (folded, scratched, etc.). There may also be document finishing options that are available in a “printer” mode, that are not available in a “copy” mode (e.g., signatures, imposition, slip sheets, tabs).
Additionally, even if the proof is not damaged, the operator of the production printer cannot simply scan the proof and use a visual display of the scanned proof in order to produce the production print. This is due to the different color spaces used by different devices. For example, the CMYK color space is the color space used for production printers and most color personal computer printers. The CMYK color space uses cyan, magenta, yellow and black inks on paper to absorb red, green and blue light. The remaining reflected light is the color perceived by the viewer. While the CMYK color space is the standard color space used by production printers, the Red-Green-Blue (RGB) color space is a personal computer's native color space.
Both RGB and CMYK color spaces are device-dependent color spaces; i.e., the colors rendered depend on the device that produces the colors. For example, the calorimetric attributes produced by a scanner vary from the colorimetric attributes visible on a monitor since a scanner uses a CCD (charge coupled device) array to capture colors, while a monitor produces colors from light-emitting phosphors. Additionally, the process of converting an image from the RGB color space to the CMYK color space generally compresses the colors into a smaller range.
The CMYK color space of one printer/device can vary significantly from the CMYK color space of another printer/device. Therefore, the CMYK color space of a first production printer can vary significantly from the CMYK color space of a second production printer. As such, ICC (International Color Consortium) profiles are frequently used to manage color between devices.
An ICC profile is a computer file that describes the color capabilities and the color space of a particular monitor, scanner, printer, printing press or color proofing device. ICC-based color management relies on two things: (1) device profiles, which characterize how individual devices produce color, and a color engine (also called a color matching module or CMM), which reads those profiles and translates and corrects colors between devices; and (2) LAB or XYZ colorimetric space, which arbitrates between color spaces of different devices. To simplify the discussion, we will only consider the LAB colorimetric space in the rest of this application. LAB colorimetric space is based on the way the human eye perceives color and is device independent. A LAB color engine translates RGB, CMYK and other color spaces to and from LAB; that is, a LAB color engine acts as an interpreter between different color spaces.
Most electronic documents to be printed or output on a particular device include multiple elements, such as text, photos, graphics and the like. Many electronic documents are a composite of other smaller documents and elements. For example, photos may be pasted into a large text document at different locations. Color graphics and monochrome images may occur on the same page of a document.
Accordingly, the individual elements of an electronic document that their colorimetric attributes are to be matched may be represented in a variety of color spaces; a situation which arises because the elements are derived from prior documents of differing origins. This situation may not be immediately apparent to the user, because the colors and other calorimetric attributes of the objects appear to match on the display or when printed using a straightforward color transformation process, such as is typical in ICC-based color management.
Based on the above background information, there exists a need for a reliable and non-time consuming system and method for matching the calorimetric attributes of a proof to a production print which overcome the drawbacks in the prior art and also provide added advantages over the prior art, such as being transparent to differing color spaces among different computing devices and among various individual elements of the proof.